1. Field of the Invention
The present invention relates to an infrared reflector which reflects infrared rays contained in sunlight and the like, as well as to a composition for forming an infrared-permeable layer which may be used in the manufacture of the infrared reflector.
2. Background Art
Common paints contain carbon black as a portion of the pigment thereof, and the degree of brightness is adjusted by the amount of this carbon black which is contained. However, when common paints which contain carbon black in this way are employed in the painting of structures which are installed outdoors, the temperature of the structure rises as a result of sunshine, and the possibility has come to be pointed out that this leads to irregularities in the operation of precision mechanical equipment.
Here, recently, paints having a strong effect of reflecting infrared rays have also been proposed. Conventional infrared-reflecting paints are paints to which a metallic oxide system pigment having a high reflectance of infrared rays, such as titanium oxide, chromium oxide, cobalt oxide, barium oxide, and the like, has been added, and by applying such paints to the target object and forming a paint film having a monolayer structure, infrared rays were reflected.
When the color of such infrared-reflecting paints was bright, it was possible to increase the amount of metallic oxide system pigment contained, and it was thus possible to increase the reflectance of the infrared rays and to suppress the increase in temperature resulting from the infrared rays; however, where the color of the paint was dark, it was necessary to reduce the proportion of the metallic oxide system pigment which represented the bright color, and reflectance decreased by this amount, and there was an increase in the rise in temperature resulting from infrared rays. Accordingly, there were problems in that the range of colors which could be produced was narrow, and in particular, there was a limit to the brightness of the color, and in usages requiring design characteristics, these are serious defects.
It is an object of the present invention to provide an infrared reflector which has superior infrared-reflecting characteristics, has a wide range of possible colors, from colors having a high degree of brightness to colors having a low degree of brightness, and which permits a high degree of design freedom, as well as to provide a composition for forming an infrared-permeable layer which may be used in the manufacture of the infrared reflector.
In order to attain the above object, the infrared reflector of the present invention has an infrared-reflecting layer and an infrared-permeable layer which is formed on this infrared-reflecting layer, and the infrared-reflecting layer has a reflectance of 60% or more, and a permeability of 25% or less (more preferably 10% or less) with respect to infrared rays having a wavelength within a range of 800 to 2600 nanometers, and the infrared-permeable layer has a reflectance of less than 60%, an absorbance of 50% or less, and a permeability of 30% or more (more preferably 50% or more) with respect to infrared rays having a wavelength of 800 to 2600 nanometers; the infrared-permeable layer contains resin components and pigments, and the amount of carbon black contained in the infrared-permeable layer is 0.1 wt % or less.
The infrared-reflecting layer may contain, in an amount within a range of 5 to 80 wt %, one or two or more selected from a group containing iron oxide powder, titanium oxide powder, scaly aluminum powder, stainless steel powder, and mica powder covered with titanium oxide, in addition to resin components.
Furthermore, the infrared-reflecting layer may be a metal layer, a white-colored glass layer, or a white-colored ceramic layer. This metal layer may be a metal film formed on the surface of a base member by plating, sputtering, vacuum deposition, ion plating, or the like. The material of the base member is not restricted; it is possible to use metal, glass, ceramic, plastic, concrete, wood, or the like.
The infrared reflector of the present invention has a structure with at least two or more layers, and the amount of carbon black employed in the pigment which strongly absorbs infrared rays having a wavelength within a range of 800 to 2600 nanometers, among the infrared rays contained in sunlight, is made extremely small. By means of this, because the absorption of infrared rays at the upper layer which serves to obtain the desired color is suppressed, while the infrared rays are reflected at the infrared-reflecting layer which is the bottom layer, despite the, fact that the range of colors possible is broad, the infrared reflectance is high. Accordingly, it is possible to apply this to the surfaces of various products and structures, and it is possible to effectively suppress the increase in temperature thereof.
The composition for forming an infrared-permeable layer of the present invention contains a resin component and pigments having an absorbance of 50% or less with respect to infrared rays having a wavelength within a range of 800 to 2600 nanometers, and the amount of carbon black contained therein is 0.1 wt % or less.
The xe2x80x9cinfrared absorbance of the pigmentxe2x80x9d referred to in the present specification is a numerical value resulting from dispersing 5 wt % of the pigment in an acrylic resin, which is a resin for paint, and forming a film having a thickness of 20 micrometers, and measuring the absorbance with respect to infrared rays having a wavelength within a range of 800 to 2600 nanometers.
By providing a coating layer on the infrared-reflecting layer having a high infrared reflectance using the composition for forming an infrared-permeable layer of the present invention, it is possible to realize a variety of colors including dark colors, while maintaining the overall high infrared reflectance.